Note: Descriptions are shown in the official language in which they were submitted.
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Technical Field
The present invention relates generally to the towing field and, morc
particularly, to an interchangeable hitch ball assembly which allows an
operator to quickly
and conveniently change from one size towing ball to another in order to meet
the needs of
any particular application.
Background of the Invention
The use of a ball joint coupling comprising a towing ball and cooperating
socket assembly in order to tow a trailer behind a towing vehicle is well
known in the art.
Such an arrangement provides the necessary freedom of movement to allow a
trailer to track
smoothly behind the towing vehicle while also providing a dependable
connection.
Over the years, towing balls of various diameters have been used for this
purpose and several industry standard sizes (e.g. 1 7/8 inch, 2 inch, 2 1/4
inch and 2 5/16
inch diameter) are now in frequent use. As a result, ii is not uncommon for a
single towing
vehicle to be used to tow various trailers where those traitors are equipped
with socket
assemblies adapted for operative connection with towing balls of different
diameters. Thus,
a need is identified for a hitch ball assembly allowing easy and convenient
interchange of
towing balls of different diameter so that the hitch of the towing vehicle may
be tailored to
fit the socket assembly of the trailer to be towed and thereby meet
application needs.
Toward this end, a number of approaches have been proposed in the past.
Representative of the interchangeable hitch ball art are U.S. Patents
4,433,854 to Smith,
5,419,576 to Van Vleet, 5,116,072 to Swenson and 4,522,421 to Vanca.
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The Smith '854 patent discloses a post for a towing ball incorporating a
spring-
biased latch pin for releasably attaching the towing ball to the base. The Van
Vleet '576
patent discloses a post and towing ball secured together by means of a
fastening pin. While
the approaches disclosed in these patents provide secure connection of the
towing ball to the
post, the latch pins prevent rotation of the towing ball relative to the post.
Such rotation 'is
desirable as it minimizes binding forces and promotes articulation and smooth
trailer
tracking at both highway speeds and when maneuvering slowly in confined areas.
The Swenson '072 patent discloses an interchangeable hitch ball assembly
including a post having an annular groove. The towing ball is secured to the
post by means
of an offset pin which extends tangentially through the annular groove so as
to allow relative
rotation of the towing ball on the post. T here, however, is some difficulty
in effectively
securing the pin in position and the structure proposed in the Swenson patent
for this
purpose is relatively expensive to produce.
The Vance '421 patent discloses an interchangeable trailer ball assembly
incorporating a mounting post including a threaded stem, a base, an axial bore
and a pair of
laterally extending bores. A tapered plunger is received in the axial bore.
The plunger is
biagcd by means of a spring into a position wherein ball bearings are forced
outwardly into
engagement with an annular groove or race in the towing ball thereby locking
the towing
ball in position on the post. An actuator rod may be extended into the axial
bore to engage
and lift the plunger so as to release the ball bearings from the groove or
race and allow
removal of the towing ball.
While very effective for its intended purpose, the interchangeable hitch ball
assembly disclosed in the Vance '42I patent does suffer several shortcomings.
First and
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foremost, secure and effective attachment of the towing ball to the post
relies entirely upon
the proper functioning of the spring. The spring, of course, has a tendency to
lose biasing
force over time as a result of wear and tear as well as exposure to the
environmental
elements. Tn extreme conditions of use and environmental temperature, the
spring may
actually fail leading directly to the failure of the connection between the
towing ball and the
post. Since the spring is completely internal and not subject to visual
inspection, the
prospect for potential problems is increased.
A need is therefore identified for an improved interchangeable hitch ball
assembly.
Sumraary of the Invention
Advantages and other novel features of the invention will be set forth in part
in
the description that follows and in part will become apparent to those skilled
in the art upon
examination of the following or may be learned with the practice of the
invention. The
advantages of the invention may be realized and obtained by means of the
instrumentalities
and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purpose
of the present invention as described herein, an improved interchangeable
hitch ball
assembly is provided. The interchangeable hitch ball assembly includes a
towing ball having
a mounting aperture and an annular race in communication with that mounting
aperture. The
interchangeable hitch ball assembly also includes a post having a base, a
threaded axial bore
and a plurality of openings in communication with that axial bore.
Additionally, the
assembly includes a plurality of ball bearings, each of the plurality of ball
bearings being
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received in one of the plurality of openings. Still further, the assembly
includes a threaded
plunger having a first segment of relatively small diameter, a second segment
of relatively
large diameter and a cam surface extending between the two segments.
The plunger is axially displaceable in the post between a first position,
wherein
the f rst segment of relatively small diameter engages the plurality of ball
bearings thereby
allowing the plurality of ball bearings to be held substantially within the
plurality of
openings of the post and a second position, wherein the second segment of
relatively large
diameter engages the plurality of ball bearings forcing the ball bearings to
project from the
openings into the annular race of the towing ball so as to secure the towing
ball to the post
while allowing the towing ball to rotate relative to the post.
Still further describing the invention, the post includes a threaded mounting
stem depending from the base. A cooperating lock washer and nut or a locknut
may be used
to engage this stem and secure the post to a hitch bar or tow bar which may be
secured to the
towing vehicle in any manner well known in the art.
Still further, the post is tapered and the mounting aperture is tapered to
match
the post. Further, the mounting aperture extends through the towing ball. The
plunger
includes a slotted head which may be engaged by a tool, such as a screwdriver,
to rotate and
thereby displace the plunger between the f rst and second positions.
Additionally, the outer
edges of the post def ning the plurality of openings are staked so as to
retain the plurality of
ball bearings in the post when the towing ball is removed to allow replacement
with another
towing ball of the same or different size as desired by the operator.
Additionally, a groove extends continuously around the second segment of the
threaded plunger and a resilient retaining ring is received in that groove. A
cooperating
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retaining channel in the post extends circumfercntially around the axial bore.
The retaining
ring carried on the plunger is partially received in this retaining channel so
as to retain the
plunger in the post and prevent its advertent removal. With the plunger held
in place, the
ball bearings arc also retained in position in the post openings.
Still other objects of the present invention will become apparent to those
skilled in this art from the following description wherein there is shown and
described a
preferred embodiment of this invention, simply by way of illustration of one
of the modes
best suited to carry out the invention. As it will be realized, the invention
is capable of other
different embodiments and its several details are capable ofmodifcation in
various, obvious
aspects all without departing from the invention. Accordingly, the drawings
and
descriptions will be regarded a~s illustrative in nature and not as
restrictive.
Brief Description of the Drawing
The accompanying drawing incorporated in and forming a part of the
specification, illustrates several aspects of the present invention and
together with the
description serves to explain the principals of the invention. In the drawing:
rigure I is a side elevational view of the present invention;
Figure 2 is a cross sectional partially exploded view along line 2-2 of Figure
1
showing the hitch ball and post of the interchangeable hitch ball assembly of
the present
invention;
Figure 3 is a detailed cross sectional view showing the secure connection of
the towing ball on the post;
Figure 3 a is a detailed perspective view of the threaded plunger; and
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Figure 4 is a partially cross sectional, side elevational view showing an
alternative embodiment of the present invention.
Reference will now be made in detail to the present preferred embodiment of.
the invention, an. example of which is illustrated in the accompanying
drawing.
Retailed Description of the Invention
Reference is now made to Figure 1-3 and 3a showing the interchangeable hitch
ball assembly 10 of the present invention. The assembly 10 includes a post
generally
designated by reference numeral 12 and a towing ball 14. As shown, the post 12
includes a
base 16. A threaded stem I8 depends firom the base. The post 12 is mounted to
a hitch bar
or draw bar B by extending the threaded stem 18 through an aperture A in the
hitch bar B so
that the base 16 rests flat on the hitch bar. A cooperating nut 20 and lock
washer 22 are then
engaged over the threaded stem 18. The nut 20 is tightened to provide a secure
connection.
The post I2 includes a tapered upper portion 24 which has an axial bore 26
and threads 28 at the lower end thereof. A plurality of openings 30 extend
through the wall
of the tapered upper portion 24 and communicate with the axial bore 26. Two
opposed
openings 30 are shown in Figure I . Preferably, other openings (not shown) are
provided in
the same plane extending radially around the circumference of the tapered
upper portion 24.
A ball bearing 32 is provided in each of the openings 30. Preferably, the
edges of the outer
wall of the tapered upper portion 24 defining the openings 30 are staked so as
to retain the
ball bearings 32 in the openings 30.
A threaded plunger 36 is secured in the axial bore 26 by engagement with a
threaded lower end 28 of the bore (see particularly Figures 3 and 3a). The
plunger 36
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includes a first segment 38 of relatively small diameter, a second segment 40
of relatively
large diameter and a cam 42 of frustoconical surface extending between the
first and second
segments. The plunger 36 is axially displaceable within the bore 26 between
first and
second positions in a manner described in greater detail below in order to
selectively secure
the towing ball 14 to the post 12 or release the towing ball from the post.
The towing ball 14 includes a mounting aperture 44 tapered to match the
tapered upper portion 24 of the post 12 and an annular race 46 extending
circumferentially
around and in communication with the mounting aperture 44. The annular race 46
is sized
axed shaped to receive the ball bearings 32 in the manner shown in Figures 2
and 3.
The mounting of the towing ball 14 on the post I2 is best illustrated with
reference to both drawing Figures 2 and 3. Specifically, the plunger 36 is
loosened from the
axial bore 26 of the post 12 and thereby displaced to the first position. This
is accomplished
by turning the plunger 36 counterclockwise with respect to the post 12. In the
first position
shown in Figure 2, the first, small diameter segment 38 of the plunger engages
the hall
bearings 32. As a result, the necessary clearance is provided i11 the axial
bore 26 to
accommodate the ball bearings 32 so that the ball bearings are fully received
within the
openings 30 and do not extend outwardly beyond the wall of the tapered upper
portion 24 of
the post 12. The towing ball 14 is then positioned downwardly in the direction
of action
arrow C. An annular shoulder 48 at the end of the mounting aperture 44 engages
the upper
edge 50 of the post 12 when the towing ball 14 is fully seated on the post 12
(see Figure 3).
In the seated position, the race 46 in the towing ball 14 is provided in the
same plane with
the openings 30 and ball bearings 32 in the post 12.
The towing ball 14 is secured in position on the post 12 by tightening the
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plunger 36 in the axial bore 26 of the post 12. Specifically, a cylindrical
opening 52 is
provided in the top of the towing ball 14 in communication with the mounting
aperture 44.
The plunger 36 includes a slotted head 54 at the upper end thereof. The
cylindrical opening
52 is sized to provide just sufficient clearance to receive the head 54 of the
plunger 36. The
slotted liead 54 of the plunger may be engaged with a screwdriver or other
tool and tightened
by turning clockwise relative to the post 12. Threads 56 on the plunger 36
engage and
cooperate with the threads 28 on the upper portion 24 of the poll 12. As a
consequence, the
plunger 36 is displaced into the second position shown in Figure 3.
As the plunger 36 is tightened, the cam surface 42 engages the ball bearings
32
forcing the ball bearings to project outwardly through the wall of the tapered
upper portion
24 of the post 12 so that they extend into the race 46 provided in the towing
ball 14. Once
the plunger 36 is fully engaged in the second position, the second, relatively
large diameter
segment 40 of the plunger 36 substantially fills the axial bore 26 so that the
ball bearings 32
are maintained in the projected position in full engagement with the race 46
of the towing
ball 14. This ensures secure connection of the towing ball 14 with the post 12
. In addition,
the ball bearings 32 and race 46 cooperate to allow relative rotation of the
towing ball 14 on
the post 12. This rotation helps ensure binding-free towing and smooth trailer
tracking
under substantially any foreseeable operating conditions. This relative
rotation prevents the
ball 14 from freezing in place and reduces the wear on the ball and the
trailer socket.
Further, since the towing ball 14 turns freely on the post 12 during towing
operation, the
turning movement of. the trailer does not turn the post 12 and any resulting
inadvertent
loosening of the nut 20 from the stem 18 of the post is avoided.
As also shown in Figure 3, the plunger 36 includes a groove 58 that extends
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continuously around the second segment 40 of the threaded plunger 36. A
resilient split
retaining ring 6U is received in the groove 58. A cooperating retaining
channel 62 extends
circumferentially around the axial bore 26 in the post 12. During installation
of the threaded
plunger 36 in the post 12, the resilient retaining ring 6U is sciueezed so as
to_be fully received
in the groove 58 and pass down in the axial bore 26. Upon reaching the
retaining channel
62, the retaining ring 60 expands under resilient memory so as to be partially
received is the
retaining channel.
The retaining channel 62 is of sufficient height to allow the plunger 36 to be
fieely adjusted between the first and second positions. This arrangement,
however, prevents
the plunger 36 from being inadvertently removed from the post 12.
Specifically, the
retaining ring 60 and retaining channel 62 function to capture the plunger 36
in the post 12.
When the plunger 36 is loosened from the post 12, the retaining ring 60
engages both the
groove 58 in the plunger 36 and the upper wall 64 of the channel 62 thereby
preventing
plunger removal. As a result, not only is the plunger 36 retained in the post
12, but the ball
bearings 32 are retained in the openings 30.
In an alternative embodiment shown in Figure 4, the retaining ring 60 and
retaining channel 62 are replaced with an annular channel 58 which receives a
rubber o-ring
60. When the plunger 36 is tightened in the axial bore 26 of the post 12, this
o-ring 60
engages the inner sidewall of the upper portion 24 of the post 12 so as to
seal out dirt and
moisture and also dampen any vibration that might otherwise have a tendency to
loosen the
plunger. Of course, the trailer towing socket overlying the hitch ball and the
weight of the
trailer itself also prevent plunger removal during use.
Tf the operator needs to change the towing ball 14 for any reason, this may be
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conveniently and easily accomplished in a quick and efficient manner. First,
the plunger 36
is loosened or backed out from the axial bore 26 of the post 12 into the first
position shown
in Figure 2 by turning counterclockwise with respect to the post 12. As a
result, the first
relatively small diameter segment 38 of the plunger 36 is again provided in
alignment with
the ball bearings 32. As a result, sufficient clearance then exists in the
axial bore 26 to
accommodate the ball bearings 32. Thus, as the towing ball 14 is lifted in the
direction of
action arrow D from the post 12, the ball bearings 32 are accommodated in the
axial bore 26
and no longer project outwardly from the wall of the tapered upper portion 24
of the post 12.
Accordingly, the towing ball 14 is easily removed. The operator then selects a
new towing
ball 14 for installation on the post 12 and that installation is completed in
the manner already
described.
The foregoing description of a preferred embodiment of the invention has been
presented for purposes of illustration and description. 1t is not intended to
be exhaustive or
to limit the invention to the precise form disclosed. Obvious modifications or
variations are
possible in light of the above teachings. The embodiment was chosen and
described to
provide the best illustration of the principles of the invention and its
practical application to
thereby enable one of ordinary skill in the art to utilize the invention in
various embodiments
and with various modifications as are suited to the particular use
contemplated. All such
modifications and variations are within the scope ofthe invention as
determined by the
appended claims when interpreted in accordance with the breadth to which they
axe fairly,
legally and equitably entitled.
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